Prof Christopher Smeenk

Prof Chris Smeenk is a professor of philosophy at Western University (London, Ontario), associate director of the Rotman Institute for Philosophy, and associate editor of Philosophy of Science. He is most well-known for his pioneering work on the philosophy of cosmology, especially as co-PI of the Templeton project “New Directions in Philosophy of Cosmology”. His Beth Lecture will present work from a book with the same title that he is currently writing together with Jim Weatherall for Oxford University Press.

The Aim and Structure of Cosmological Theory

The ΛCDM model incorporates three major components requiring new fundamental physics: dark energy, dark matter, and the physics of the early universe. Each faces variants of Duhem’s underdetermination problem: how do we establish that particular theoretical representations have genuine physical significance, and which aspects of these theories actually contribute to their empirical success? Drawing on George Smith’s framework of “closing the loop,” I argue that addressing Duhem’s challenge requires sustained cycles of prediction, measurement, and theoretical refinement that progressively constrain viable models and identify novel robust features of the target system. Using early universe cosmology as a detailed case study, I examine whether and how this standard can be met in cosmology. Currently there are a number of inflationary models, differing in underlying physical features, compatible with observations. This flexibility reflects how inflationary models are constructed without tight constraints from more fundamental physics.  And in light of this flexibility the evidential case that an inflationary stage occurred is much weaker.  I will consider, following the closing the loop methodology, two ways to address this challenge: establishing a connection to independent constraints from quantum gravity or particle physics, or identifying a unique mechanism enabling discovery of novel robust features. Contrasting inflation with more successful areas of cosmology illuminates what closing the loop requires and the distinctive challenges facing ΛCDM’s theoretical components.